/*
 *    Copyright 2009-2022 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.scripting.xmltags;

import java.util.List;

/**
 * @author Clinton Begin
 */
// 相当于java中的switch语句。when标签相当于case，otherwise相当于default
/*
 * <choose>
 *       <when test="ids != null and ids.size() > 0">
 *         <where>
 *           <foreach collection="ids" open="id in ( " close=")" separator="," item="id">
 *             #{id}
 *           </foreach>
 *         </where>
 *       </when>
 *       <otherwise>
 *         where 0
 *       </otherwise>
 *     </choose>
 */
public class ChooseSqlNode implements SqlNode {
  // 用来保存otherwise标签的内容
  private final SqlNode defaultSqlNode;
  // 用来保存when标签的内容
  private final List<SqlNode> ifSqlNodes;

  public ChooseSqlNode(List<SqlNode> ifSqlNodes, SqlNode defaultSqlNode) {
    this.ifSqlNodes = ifSqlNodes;
    this.defaultSqlNode = defaultSqlNode;
  }

  @Override
  public boolean apply(DynamicContext context) {
    // 遍历when标签
    for (SqlNode sqlNode : ifSqlNodes) {
      // 这个标签成立，直接跳过其他标签
      if (sqlNode.apply(context)) {
        return true;
      }
    }
    // 如果存在otherwise标签，且所有when标签都不成立，就执行otherwise标签的内容
    if (defaultSqlNode != null) {
      defaultSqlNode.apply(context);
      return true;
    }
    return false;
  }
}
